Here are some documents that might be difficult to find elsewhere.
SP4: A Transport Encapsulation Security Protocol "SP4: A Transport Encapsulation Security Protocol." In Tenth National Computer Security Conference Proceedings, September 1987, pp 158-161. | |
SDNS Security Protocol 4 (SP4), Revision 1.3, 2 May 1989 The Layer 4 Security Protocol developed as part of the US National Security Agency's Secure Data Network System (SDNS) program. | |
SDNS Message Security Protocol (MSP), Revision 1.5, 1 August 1989 The Message Security Protocol developed as part of the US National Security Agency's Secure Data Network System (SDNS) program. | |
The X.500 Directory attributes that support the Message Security Protocol developed as part of the US National Security Agency's Secure Data Network System (SDNS) program. |